This contribution is a written version of my closing talk https://indico.cern.ch/event/433345/contributions/2321629/attachments/1411355/2158856/ZajcQM17.pdf presented at the Quark Matter 2017 ...https://indico.cern.ch/event/433345/ conference. Neither the talk nor this contribution to the conference proceedings is intended as a comprehensive summary1. Rather, a brief discussion is presented of emerging themes and challenges in the field of relativistic heavy ion physics. 1Those seeking such a summary should consult Jürgen Schukraft's masterful overview 3 in the opening talk of the conference.
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The peak of the two-particle Bose-Einstein correlation functions has a very interesting structure. It is often believed to have a multivariate Gaussian form. We show here that for the class of stable ...distributions, characterized by the index of stability \(0 < \alpha \le 2\), the peak has a stretched exponential shape. The Gaussian form corresponds then to the special case of \(\alpha = 2\). We give examples for the Bose-Einstein correlation functions for univariate as well as multivariate stable distributions, and we check the model against two-particle correlation data.
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Collisions of heavy nuclei at very high energies offer the exciting possibility of experimentally exploring the phase transformation from hadronic to partonic degrees of freedom which is predicted to ...occur at several times normal nuclear density and/or for temperatures in excess of
∼
170
MeV
. Such a state, often referred to as a quark-gluon plasma, is thought to have been the dominant form of matter in the universe in the first few microseconds after the Big Bang. Data from the first five years of heavy ion collisions of Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) clearly demonstrate that these very high temperatures and densities have been achieved. While there are strong suggestions of the role of quark degrees of freedom in determining the final-state distributions of the produced matter, there is also compelling evidence that the matter does
not behave as a quasi-ideal state of free quarks and gluons. Rather, its behavior is that of a dense fluid with very low kinematic viscosity exhibiting strong hydrodynamic flow and nearly complete absorption of high momentum probes. The current status of the RHIC experimental studies is presented, with a special emphasis on the fluid properties of the created matter, which may in fact be the most perfect fluid ever studied in the laboratory.
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Experimental measurements in relativistic collisions of small systems from $p + p$ to $p/d/ ^3He + A$ at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) reveal particle ...emission patterns that are strikingly similar to those observed in $A + A$ collisions of large nuclei. One explanation of these patterns is the formation of small droplets of quark-gluon plasma (QGP) followed by hydrodynamic evolution. A geometry engineering program was proposed to further investigate these emission patterns, and the experimental data from that program in $p + Au, d + Au, ^3 He + Au$ collisions for elliptic and triangular anisotropy coefficients $v_2$ and $v_3$ follow the pattern predicted by hydrodynamic calculations C. Aidala et al. (PHENIX Collaboration), Nat. Phys. 15, 214 (2019). One alternative approach, referred to as initial-state correlations, suggests that for small systems the patterns observed in the final-state hadrons are encoded at the earliest moments of the collision and therefore require no final-state parton scattering or hydrodynamic evolution. Recently, new calculations using only initial-state correlations, in the dilute-dense approximation of gluon saturation physics, reported striking agreement with the $v_2$ patterns observed in $p/d/ ^3He + Au$ data at RHIC M. Mace, V. V. Skokov, P. Tribedy, and R. Venugopalan, Phys. Rev. Lett. 121, 052301 (2018). The results reported by Mace, Skokov, Tribedy and Venugopalan (MSTV) are counterintuitive and thus we aim here to reproduce some of the basic features of these calculations. In this first investigation, we provide a description of our publicly available model, ip-jazma, and investigate its implications for saturation scales, multiplicity distributions, and eccentricities, reserving for later work the analysis of momentum spectra and azimuthal anisotropies. We find that our implementation of the saturation physics model reproduces the results of the MSTV calculation of the multiplicity distribution in $d + Au$ collisions at RHIC. However, additional aspects of studies, together with existing data, call into question some of the essential elements reported by MSTV. Resolution of these issues will require further developments of ip-jazma, in order to determine if it can replicate the qualitative agreement with the $v_2$ reported by MSTV. Both the work reported here and future studies will establish which features in the experimental data are uniquely attributable to the color glass condensate description.
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6.
A reaction plane detector for PHENIX at RHIC Richardson, E.; Akiba, Y.; Anderson, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2011, Volume:
636, Issue:
1
Journal Article
Peer reviewed
Open access
A plastic scintillator paddle detector with embedded fiber light guides and photomultiplier tube readout, referred to as the Reaction Plane Detector (RXNP), was designed and installed in the PHENIX ...experiment prior to the 2007 run of the Relativistic Heavy Ion Collider (RHIC). The RXNP's design is optimized to accurately measure the reaction plane (RP) angle of heavy-ion collisions, where, for mid-central sNN=200GeV Au+Au collisions, it achieved a 2nd harmonic RP resolution of ∼0.75, which is a factor of ∼2 greater than PHENIX's previous capabilities. This improvement was accomplished by locating the RXNP in the central region of the PHENIX experiment, where, due to its large coverage in pseudorapidity (1.0<|η|<2.8) and ϕ(2π), it is exposed to the high particle multiplicities needed for an accurate RP measurement. To enhance the observed signal, a 2-cm Pb converter is located between the nominal collision region and the scintillator paddles, allowing neutral particles produced in the heavy-ion collisions to contribute to the signal through conversion electrons. This paper discusses the design, operation and performance of the RXNP during the 2007 RHIC run.
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The new millennium's qualitative advances in relativistic heavy ion physics are in part due to, and are in part causing, a new appreciation for quantitative rigor in both experimental and theoretical ...work in the field. In these proceedings for the conference-opening “pre-Summary” talk I present an annotated guide to the figures and points made in my talk
http://qm09.phys.utk.edu/indico/getFile.py/access?contribId=491&sessionId=25&resId=0&materialId=slides&confId=1.
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Recently, multiparticle-correlation measurements of relativistic p/d/^{3}He+Au, p+Pb, and even p+p collisions show surprising collective signatures. Here, we present beam-energy-scan measurements of ...two-, four-, and six-particle angular correlations in d+Au collisions at sqrts_{NN}=200, 62.4, 39, and 19.6 GeV. We also present measurements of two- and four-particle angular correlations in p+Au collisions at sqrts_{NN}=200 GeV. We find the four-particle cumulant to be real valued for d+Au collisions at all four energies. We also find that the four-particle cumulant in p+Au has the opposite sign as that in d+Au. Further, we find that the six-particle cumulant agrees with the four-particle cumulant in d+Au collisions at 200 GeV, indicating that nonflow effects are subdominant. These observations provide strong evidence that the correlations originate from the initial geometric configuration, which is then translated into the momentum distribution for all particles, commonly referred to as collectivity.
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This contribution is a reprise of my summary talk at the conference, attempting to capture the experimental status of flavor dynamics in relativistic heavy ion collisions circa October 2008.
We present measurements of the cross section and double-helicity asymmetry ALL of direct-photon production in p→+p→ collisions at s=510 GeV. The measurements have been performed at midrapidity (|η|
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